“Inflame” – to set fire.
Inflammation is “A dynamic response of
vascularised tissue to injury.”
It is a protective response.
It serves to bring defense & healing mechanisms to
the site of injury.
What is Inflammation?
A reaction of a living tissue & its micro-circulation
to a pathogenic insult.
A defense mechanism for survival .
Reaction of tissues to injury, characterized clinically
by: heat, swelling, redness, pain, and loss of function.
Pathologically by : vasoconstriction followed by
vasodilatation, stasis, hyperemia, accumulation of
leukocytes, exudation of fluid, and deposition of fibrin.
How Does It Occur?
• The vascular & cellular responses of inflammation
are mediated by chemical factors (derived from
blood plasma or some cells) & triggered by
• Tissue injury or death ---> Release mediators
Cardinal Signs of Inflammation
Redness : Hyperaemia.
Warm : Hyperaemia.
Pain : Nerve, Chemical
Swelling : Exudation
Loss of Function: Pain
Acute inflammation: Less than 48 hours
Chronic inflammation: Greater than 48 hours
(weeks, months, years)
Acute inflammation: Neutrophils
Chronic inflammation: Mononuclear cells
(Macrophages, Lymphocytes, Plasma cells).
Pathogenesis: Three main processes occur at the site
of inflammation, due to the release of chemical
Increased blood flow (redness and warmth).
Increased vascular permeability (swelling, pain &
loss of function).
Mechanism of Inflammation
1. Vaso dilatation
2. Exudation - Edema
3. Emigration of cells
The major local manifestations of
acute inflammation, compared
(1)Vascular dilation and
increased blood flow (causing
erythema and warmth).
(2) Extravasation and deposition of
plasma fluid and proteins
(3) leukocyte emigration and
accumulation in the site of
Changes in vascular flow (hemodynamic
Slowing of the circulation
outpouring of albumin rich fluid into the extravascular
tissues results in the concentration of RBCs in small
vessels and increased viscosity of blood.
Neutrophi become oriented at the periphery of vessels
and start to stick.
minor damage---- 15-30 minutes
severe damage---- a few minutes
Lymphatics in inflammation:
Lymphatics are responsible for draining edema.
Edema: An excess of fluid in the interstitial tissue
or serous cavities; either a transudate or an
• An ultrafiltrate of blood plasma
–permeability of endothelium is usually
–low protein content ( mostly albumin)
• A filtrate of blood plasma mixed with
inflammatory cells and cellular debris.
–permeability of endothelium is usually altered
–high protein content.
• A purulent exudate: an inflammatory exudate
rich in leukocytes (mostly neutrophils) and
parenchymal cell debris.
Divided into 4 steps
Margination, rolling, and adhesion to endotheliumMargination, rolling, and adhesion to endothelium
Diapedesis (trans-migration across the endothelium)Diapedesis (trans-migration across the endothelium)
Migration toward a chemotactic stimuli from theMigration toward a chemotactic stimuli from the
source of tissue injury.source of tissue injury.
3 distinct steps
Recognition and attachment
Killing or degradation
Chemical substances synthesised or released and
mediate the changes in inflammation.
Histamine by mast cells - vasodilatation.
Prostaglandins – Cause pain & fever.
Bradykinin - Causes pain.
Acute inflammation has one of four
• Abscess formation
• Progression to chronic inflammation
• Resolution--tissue goes back to normal
• Repair--healing by scarring or fibrosis
• "A localized collection of pus (suppurative
inflammation) appearing in an acute or chronic
infection, and associated with tissue destruction,
• Site: skin, subcutaneous tissue, internal organs like
brain, lung, liver, kidney,…….
• Pathogenesis: the necrotic tissue is surrounded by
pyogenic membrane, which is formed by fibrin and
help in localize the infection.
- It is an extensive form of abscess in which pus
is present in multiple loci open at the surface
- Occur in the back of the neck and the scalp.
Furuncle or boil
- It is a small abscess related to hair
follicles or sebaceous glands, could
be multiple furunclosis.
- It is an acute diffuse suppurative inflammation caused
by streptococci, which secrete hyaluronidase &
streptokinase enzymes that dissolve the ground
substances and facilitate the spread of infection.
- Areolar tissue; orbit, pelvis, …
- Lax subcutaneous tissue